The present invention relates to an electric drive spindle.
In particular, the present invention relates to an electric drive spindle of the type comprising an electric motor provided with a tubular output shaft defining a tool-carrier spindle; attachment means associated with the said spindle to fix a tool axially to the spindle itself; and a plurality of actuator means to drive the spindle to rotate about its own axis and to displace the attachment means with respect to the spindle, between a position in which it locks the tool onto the spindle and a release position.
Generally, in use, known electrical drive spindle of the above-described type perform different operating sequences the practicability of which is tied to particular operating conditions of the tool itself. For example, the displacement of the attachment means to the release position must be prevented when the spindle is in motion. Consequently, for the purpose of guaranteeing operation in complete safety and efficiency of the electric drive spindle, operating parameters such as the different positions of the various members constituting the attachment means and the speed of rotation of the spindle must be continuously monitored.
In general, in known electric drive spindles of the above-described type, the monitoring of the above-mentioned operating parameters is effected by means of a plurality of sensors (at least four), normally of the inductive type, which are mounted on the associated electric drive spindle and the axial position of which on the axis of rotation of the spindle must be adjusted manually from the outside.
Moreover, in that the dimensions of the machines on which drive spindles are installed must be maintained within determined values, the drive spindles themselves must normally be disposed in relatively small spaces to which, however, it is necessary to be able to gain access from the outside in order to be able to perform the said adjustments on the axial position of the said sensors.
From the above explanation it results that the known drive spindles of the type described above are relatively expensive because of the high number of sensors utilised, and relatively complex in that the adjustment operations of the said inductive sensors are made particularly complicated and lengthy both because of their high number and because of the relatively narrow spaces in which the drive spindles themselves are housed.
The object of the present invention is to provide a drive spindle which will be free from the above-explained disadvantages.
According to the present invention there is provided a drive spindle comprising a tool-carrier spindle; attachment means for axially fixing a tool to the said spindle; and a plurality of actuator means to drive the said spindle to rotate about its axis and to actuate the said attachment means between a position in which the said tool is locked on the said spindle, and a release position; each said actuator means comprise at least one movable member able to vary its state (angular and/or axial position) with respect to the said axis; and monitoring means provided to monitor the said actuator means; characterised in that at least one said movable member is a reference member formed and disposed such a way as to detect the state of all the other movable members, and in that the said monitoring means comprise a single sensor, preferably an optical sensor comprising a plurality of CCD sensors disposed in a row parallel to a displacement direction of the said reference member and operable to detect the state of the said reference member.
In a preferred embodiment of the above-defined drive spindle the said attachment means comprise a grip member rotatable with the said spindle about the said axis and operable to engage a shank of the said tool, and the said actuator means comprise first actuator means for driving the said spindle to rotate about the said axis and second actuator means for displacing the said grip member between the said locking position and the said release position; the said reference member forming part of the said second actuator means.
In particular, preferably, the said first actuator means comprise an electric motor provided with a tubular output shaft which is coaxial with the said axis and defines the said spindle; the said reference member comprising a support rod connected to the said grip member and housed in the said tubular shaft for rotation therewith; the said rod being couple axially slidably to the said tubular shaft to displace the said grip member between the said locking position and the said release position.